932 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



pappus in the pistillate flowers of copious capillary bristles, in the 

 staminate flowers of scabrous, often twisted, clavellate bristles. 



Most of the species are browsed at times, but their palatability is 

 generally low and some of them (B. pteronioides, B. sarothroides) are 

 reputed poisonous to livestock. The widely distributed and very 

 common seepwillow (B. glutinosa) is recommended for erosion control, 

 along water courses, because of its deep, widespreading root system 

 and its tendency to form thickets. It is stated to be readily propa- 

 gated by cuttings. 



Key to the species 



1. Plants low (usually 60 cm. high or less), woody only at base; leaves all small 

 (mostly less than 1 cm. long) , narrow, entire (2) . 

 2. Plant glabrous; involucre 6 to 10 mm. high; pistillate pappus deep brown 

 or purplish brown 1. B. wrightii. 



2. Plant densely hispidulous or hirtellous ; involucre 6 mm. high or less ; pistillate 



pappus merely brownish-tinged 2. B. brachyphylla. 



1. Plants either much taller, or definitely woody-stemmed, or the leaves con- 

 spicuously toothed (3) . 



3. Heads solitary at the tips of very short leafy branchlets, these racemosely 



arranged along the branches; larger leaves mostly obovate and sharply 

 toothed, those of the flowering branchlets minute and entire. 



3. B. PTERONIOIDES. 



3. Heads otherwise arranged (4). 



4. Broomlike shrubs, with numerous, erect, strongly sulcate- angled branches; 



leaves usually essentially absent at flowering time, if present, then 



mostly obovate or spatulate and usually entire (5) . 



5. Pistillate pappus very short, 3 to 4 mm. long, scarcely or not surpassing 



the styles ; receptacle often rounded or elevated, usually bearing some 



pales between the flowers, at least in the pistillate head; staminate 



heads 2.5 to 4 mm. high 4. B. sergiloides. 



5. Pistillate pappus elongate in fruit (10 mm. long or more), much sur- 



passing the styles; receptacle flattish, deeply alveolate but not bear- 

 ing pales; staminate heads 3.5 to 7 mm. high- _ 5. B. sarothroides. 

 4. Plants not broomlike (or sometimes somewhat so in B. emoryi) ; leaves 

 normally present at flowering time, usually toothed (6). 



6. Pistillate pappus in fruit elongate, surpassing the styles by 3 mm. or 



more (7). 

 7. Larger leaves cuneate-oblanceolate or oblong-oblanceolate, 3 to 18 

 mm. wide, distinctly 3-nerved; involucre 4 to 8 mm. high. 



6. B. EMORYI. 



7. Larger leaves mostly linear or narrowly oblanceolate, 3 to 8 mm. 



wide, usually 1-nerved; involucre 3 to 4 mm. high. 



7. B. NEGLECTA. 



6. Pistillate pappus in fruit not elongate, scarcely or not surpassing the 

 styles (8). 



8. Leaves narrowly linear or linear-lanceolate, 1.5 to 8 mm. wide, 



usually closely, evenly, and sharply spinulose-serrulate. 



8. B. THESIOIDES. 



8. Leaves from lanceolate or elliptic to cuneate-obovate, entire or 

 rather coarsely or unevenly toothed, the teeth not spinulose (9). 

 9. Leaves cuneate-oblong to oblong-oblanceolate, rather coarsely and 

 unequally toothed, 1.5 to 3.5 cm. long, 4 to 15 mm. wide. 



9. B. BIGELOVII. 



9. Leaves mostly lanceolate or elliptic-lanceolate, 5 to 15 cm. long, 

 entire or evenly toothed (10). 

 10. Heads in a cymose panicle terminating the stem; leaves usually 



toothed 10. B. glutinosa. 



10. Heads in small cymose panicles terminating numerous short 

 lateral branches as well as the main stem; leaves mostly 

 entire 11. B. viminea. 



